Total Body Irradiation has been shown to cause striking regression of disease in chronic lymphocytic leukemia (CLL) and in non-Hodgkin's lymphoma (NHL). The time course of the response, particularly in NHL, suggests that mechanisms other than radiation-induced cell death may be involved, and further that the mechanisms may be immunologic. The time course of response, 6-8 weeks in NHL and 6-12 months in CLL, are such that these diseases also become suitable models in which to develop and test serial immunologic monitoring techniques. This study was initiated in order to: 1. develop tests of immunologic function which are sufficiently reproducible, and sensitive to detect alterations in immune function induced by therapy and/or change in disease status; and 2. apply these tests in a situation where it is likely that one may be able to assess the relative contributions of therapy and level of immune function to change in disease status.